1. Field of the Invention
The invention relates to a roof vent for a flat roof. More particularly, the invention relates to a roof vent with a moisture detector for the early detection of a roof leak and to a roof system incorporating several such vents.
2. State of the Art
Commercial, industrial, and institutional flat roof systems generally include several layers of material, i.e., a deck covered with lightweight insulating concrete, a vapor barrier covering the concrete, roofing insulation material covering the vapor barrier, a moisture barrier roof membrane covering the roofing insulation material, and a top layer of gravel, tar, ballast, etc. These watertight roof systems are generally effective at preventing water from passing through the roof system into the building. However, these systems can and do leak due to damage, material failure, or poor workmanship. When these types of roof systems leak, moisture tends to become trapped between the layers of the system where it remains undetected until substantial damage is done.
In order to prevent moisture from being trapped between the layers of a roof system, it is common to provide vents spaced throughout the roof system. FIG. 1 shows a prior art roof vent and FIG. 2 shows the vent installed in a conventional prior art roof system. The known vent 10 generally includes a circular base flange 12, an upstanding hollow frustroconical body 14 terminating with a cap 15, the cap and the body defining an annular opening into the body 14. The vent 10 is installed in a conventional roofing system 17 which may include, e.g., a deck 18, insulating concrete 26, a vapor barrier 23, and an upper waterproof membrane 22. The vent 10 is located such that the flange 12 is on top of the waterproof membrane 22 and is covered with flashing 24. The membrane 22 and the flashing 24 are covered with gravel, tar, ballast, etc. 25.
My prior U.S. Pat. No. 5,193,390, the complete disclosure of which is hereby incorporated herein by reference, discloses a modified roof vent and roof system which includes moisture detectors and moisture indicators. Prior art FIGS. 3-6 show the roof vents and roof system of the '390 patent. The roof vent 30 generally includes a circular base flange 34 with an upstanding hollow frustroconical body 32. The body 32 terminates with a cap 36 which is held in place by clamps 38 and which has a removable cover 36a. The cap 36 is provided with a shoulder 39 having openings 42 which provide a vapor passage to the interior of the body 32 via a hole 44 in a lower platform 46 of the cap 36. Preferably, a one-way diaphragm 45 is provided below the hole 44 which permits moisture to exit the body 32 but prevents moisture from entering. The cap 36 and the body 32 are sealed by mutually engaging ridges 48, 52.
As seen in prior art FIG. 3, the cap 36 has three interior platforms: lower platform 46, intermediate platform 54, and upper platform 58. The intermediate platform 54 includes a moisture indicator device or circuit 56 and the upper platform 58 includes a display 62 for indicating moisture such as a movable needle 64 which is coupled via an opening 66 to the device 56. The circuit or device 56 is electrically coupled to at least one moisture sensing element 68 by insulated conductors 72, 74. Moisture sensing elements of the type described in U.S. Pat. No. 4,110,945; 4,598,273; or 4,723,109 may be used and these prior U.S. patents are therefore incorporated herein by reference for their teaching of moisture sensors.
The vent 30 is installed in a roof system 63 as shown in prior art FIG. 4. The roof system 63 generally includes a deck 18' which is covered with a vapor barrier 23' which is covered with insulation 26' which is covered with a waterproof membrane 22'. The vent 30 is located with its flange 34 on top of the membrane 22' and an opening is made in the insulation 26' beneath the body 32 so that the moisture sensing element 68 may be placed directly upon the vapor barrier 23'. Preferably, a second moisture sensing element 76 is located between the insulation 26' and the waterproof membrane 22'. Both sensing elements are coupled in parallel to the indicator circuit 56.
The vent and roof system of my prior patent are effective in providing an early warning of roof leakage and in indicating where in a roof system a leak exists. According to the embodiment described (and illustrated in FIGS. 3 and 4, a periodic visual inspection is made of a roof where the cover 36a of each vent cap 36 is removed and the moisture indicator is inspected to determine whether the moisture sensing elements associated with the vent 30 are detecting moisture. A more sophisticated embodiment of my earlier invention is shown in prior art FIGS. 5 and 6. There each vent 80 is provided with a radio transmitter 82 and a radio receiver 84 is provided. According to this embodiment, each transmitter 82 transmits a unique signal when moisture is detected so that the receiver 84 will indicate not only that the roof 63 is leaking, but will indicate the approximate location of the leak.
The vent and roof system of my earlier patent work very well to achieve the objects for which they were designed. It is my intention to improve my earlier invention by making it more economical so that it may be utilized in a wider range of applications.